Question: Expand.
Answer: $\begin{aligned} ( x{-5})(x-4)&= x(x-4){-5}(x-4) \end{aligned}$ $\begin{aligned} \phantom{( x{-5})(x-4)}&=x^2-4x-5x+20 \\\\ &=x^2-9x+20 \end{aligned}$